Enabling simultaneous use of home network and foreign network by a multihomed mobile node

ABSTRACT

The invention relates to a method performed by a home agent serving a mobile node in a home network upon attachment of a mobile node to the home network as well as to the home agent. The invention also relates to a method for enabling simultaneous use of a plurality of interfaces by a mobile node being attached to a home network through one of the plurality of interfaces and to at least one foreign network through at least another interface of the plurality of interfaces. Moreover, the invention provides a mobile node and a proxy acting on behalf of the mobile node. To enable a mobile node to use a home network and at least one foreign network for communications the invention suggests the registration of the mobile node&#39;s home address or of a network node&#39;s address within its home network as a care-of address in the home network.

This is a continuation of U.S. application Ser. No. 13/484,106 filed May30, 2012, which is a continuation of U.S. application Ser. No.13/040,075 filed Mar. 3, 2011, now U.S. Pat. No. 8,219,708, which is adivisional of U.S. application Ser. No. 12/067,110 filed Jun. 2, 2008,now U.S. Pat. No. 8,078,753, which is a national stage ofPCT/EP2006/008128 filed Aug. 17, 2006, which is based on EuropeanApplication No. 05020354.6 filed Sep. 19, 2005, the entire contents ofeach which are incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to a method performed by a home agent serving amultihomed mobile node in a home network of the multihomed mobile nodeupon attachment of a multihomed mobile node to the home network as wellas to the home agent. Further, the invention also relates to a methodfor enabling simultaneous use of a plurality of interfaces by amultihomed mobile node being attached to a home network through one ofthe plurality of interfaces and to at least one foreign network throughat least another interface of the plurality of interfaces. Moreover, theinvention provides a multihomed mobile node and a proxy acting on behalfof the multihomed mobile node.

TECHNICAL BACKGROUND Long Term Evolution (LTE)

Third-generation mobile systems (3G) based on WCDMA radio-accesstechnology are being deployed on a broad scale all around the world. Afirst step in enhancing or evolving this technology entails introducingHigh-Speed Downlink Packet Access (HSDPA) and an enhanced uplink, alsoreferred to as High Speed Uplink Packet Access (HSUPA), giving aradio-access technology that is highly competitive.

However, knowing that user and operator requirements and expectationswill continue to evolve, the 3GPP has begun considering the next majorstep or evolution of the 3G standard to ensure the long-termcompetitiveness of 3G. The 3GPP launched a Study Item “Evolved UTRA andUTRAN” (E-UTRA and E-UTRAN). The study will investigate means ofachieving major leaps in performance in order to improve serviceprovisioning and reduce user and operator costs.

It is generally assumed that there will be a convergence toward the useof Internet Protocols (IP), and all future services will be carried ontop of IP. Therefore, the focus of the evolution is on enhancements tothe packet-switched (PS) domain.

The main objectives of the evolution are to further improve serviceprovisioning and reduce user and operator costs as already mentioned.

More specifically, some key performance and capability targets for thelong-term evolution are:

-   -   Significantly higher data rates compared to HSDPA and HSUPA:        envisioned target peak data rates of more than 100 Mbps over the        downlink and 50 Mbps over the uplink;    -   Improved coverage: high data rates with wide-area coverage;    -   Significantly reduced latency in the user plane in the interest        of improving the performance of higher layer protocols (for        example, TCP) as well as reducing the delay associated with        control plane procedures (for instance, session setup);    -   Greater system capacity: threefold capacity compared to current        standards.

Another key requirement of the long-term evolution is to allow for asmooth migration to these technologies.

Mobility Management

For mobility management in a system with heterogeneous access networksdifferent protocols may be applied. On the one hand global mobilityprotocols may be used for inter Access System mobility. A well-knownexample for a global mobility protocol is the client-based network layerprotocol Mobile IP (MIPv6). With this protocol the mobility istransparent on a mobile node for layers above the network layer. On theother hand local mobility protocols are used for intra Access Systemmobility, examples thereof are NetLMM or GTP. Especially these twoexamples are network-based, i.e., their use is completely transparent tothe mobile node, in particular the network layer. NetLMM is IP-based andindependent of the underlying network technology, whereas GTP isespecially for the 3GPP network and is coupled with the technology,e.g., relies on 3GPP specific identifiers.

MIPv6

Using Mobile IPv6 as specified in RFC 3775 (available athttp://www.ietf.org, incorporated herein by reference) a mobile node(MN) is reachable by its home address even when away from home. For thisthe mobile node is associated with a care-of address (CoA), whichprovides information about the mobile node's current location. The homeagent (HA) of the mobile node and also a correspondent node (CN) set upa binding between the home address and the care-of address in a cacheand packets destined for the mobile node are directly sent to thecare-of address. If the mobile node is at its home network, itderegisters the care-of address and receives packets directly with itshome address.

In order to allow a home agent to intercept traffic for a node the proxyNeighbor Advertisements of the Neighbor Discovery protocol are used.According to Mobile IPv6 if there is a binding cache entry in the homeagent for a mobile node, the home agent sends proxy neighboradvertisements so that the neighbor cache entries of the nodes in thevicinity of the home agent are updated and all traffic to the mobilenode is sent to the link-layer address of the home agent.

In the IETF (Internet Engineering Task Force) discussions are ongoinghow to enhance Mobile IPv6 to support Mobile Nodes with multipleinterfaces. This simultaneous use of the multiple interfaces increasesservice quality for the terminals and makes better use of the networkcapacity.

Mobile Node Returning “Home”

When returning home, i.e., one of the mobile node's interfaces isattached to the home link, two possible approaches are described in thestate of the art.

In the first approach the mobile node sends a binding update to the homeagent with its home address as a care-of address, the home registrationbit set and lifetime set to zero, to instruct its home agent to nolonger intercept or tunnel packets for it. In this case the home agentdeletes the binding of the mobile node from the binding cache and stopssending proxy neighbor advertisements in behalf of the mobile node. Onthe other hand the mobile node starts to send neighbor advertisementswith its own link-layer address on the home link, so that the neighborcache entries in the routers are changed and all traffic is directlysent to the mobile node.

In a second approach the mobile node de-registers the binding for theinterface on the home link and stops using the interface. In this caseall traffic previously sent to the de-registered interface is then sentto the remaining registered interface, i.e., through a foreign networkto which the mobile node is still connected.

In both scenarios it is not possible for the MN to use the home link anda foreign link simultaneously.

SUMMARY OF THE INVENTION

The object of the invention is to enable a multihomed mobile node to usea home network and at least one further foreign network forcommunications.

The object is solved by the subject matter of the independent claims.Advantageous embodiments are subject to the dependent claims.

One of the aspects of the invention is to allow a multihomed mobile nodeto register its home address as a care-of address in its home networkwhen being connected thereto. Alternatively, an address of a networknode in the home network may be registered in the binding cache of themultihomed mobile node's home agent. Another aspect of the invention isto allow a multihomed mobile node to register plural care-of addressesat its home agent which may include the multihomed mobile node's homeaddress or an address in the home network.

One embodiment of the invention relates to a method performed by a homeagent serving a multihomed mobile node in a home network of themultihomed mobile node upon attachment of a multihomed mobile node tothe home network. The home agent may receive a binding update messagefor registering an address in the home network as a care-of address forthe multihomed mobile node. This address to be registered as a care-ofaddress for the multihomed mobile node in the home network is a homeaddress of the multihomed mobile node in the home network or an addressof a network node located in the home network. The network node may forexample be a proxy acting on behalf of the multihomed mobile node.Further, the home agent adds the address as a care-of address to itsbinding cache.

Adding the address to the binding cache of the home agent may forexample generate a binding for the multihomed mobile node's home addressin the home network. Further, the registration of the address as acare-of address for the multihomed mobile node in the home network mayindicate to the home agent that the multihomed mobile node is furtherattached to at least one foreign network.

In a further embodiment of the invention, the binding update comprises abinding unique identifier assigned to the binding generated byregistering the address as a care-of address of the multihomed mobilenode in the home network.

In another embodiment of the invention the binding update may comprise alifetime field that indicates a number of time units remaining beforethe binding is considered expired by the home agent. According to thisembodiment the lifetime field indicates that the binding of theregistered address as a care-of address for the multihomed mobile nodein the home network does not expire.

In a further embodiment of the invention, the binding cache furtherincludes at least one further care-of address for the multihomed mobilenode in at least one foreign network.

Moreover, according to another embodiment of the invention, the homeagent may transmit, relay or forward network layer packets to themultihomed mobile node through the home network utilizing the addressregistered as a care-of address for the multihomed mobile node in thehome network and/or through at least one foreign network to which themultihomed mobile node is further attached utilizing a care-of addressof the multihomed mobile node in the respective at least one foreignnetwork registered for the multihomed mobile node in the binding cache.

According to yet another embodiment of the invention, the home agent maytransmit or forward network layer packets to the multihomed mobile nodeutilizing at least one care-of address of the plurality of care-ofaddresses registered for the multihomed mobile node in a binding cachemaintained by the home agent.

In order to transmit, relay or forward the network layer packets to themultihomed mobile node the home agent may first resolve a link layeraddress associated with the care-of address in the binding cache from aneighbor cache maintained in the home agent so as to transmit, relay orforward the network layer packets to said resolved link layer address,e.g., by means of a link layer protocol.

In a variation of this embodiment, when forwarding or transmitting thetransport layer packets to the multihomed mobile node through the homenetwork, the resolved link layer address may be the link layer addressof the multihomed mobile node on its interface to the home network or alink layer address of an intermediate node in the downlink distributionpath between home agent and the multihomed mobile node.

In a further variation of the embodiment the network layer packets areforwarded or transmitted to the multihomed mobile node using the homenetwork specific layered protocol structure of the user plane. This mayfor example include sending the network data packets to the multihomedmobile node via an intermediate node in the downlink distribution pathbetween home agent and the multihomed mobile node.

Further, in another variation of the embodiment, the home agent mayreceive a message indicating the intermediate node's link layer addressand the home agent may update the neighbor cache thereby associating theintermediate node's link layer address with the registered care-ofaddress associated with the address in the binding update.

In a further embodiment of the invention the home agent maintains abinding cache comprising a plurality of care-of addresses registered forthe multihomed mobile node, wherein the plurality of care-of addressesincludes said address comprised in the binding update. Moreover, thehome agent may decide which care-of address or which care-of addressesto utilize for transmitting or forwarding network layer packets to themultihomed mobile node based on filter policies.

The filter policies may for example comprise at least one of userpreferences, network operator preferences, source and destination IPaddresses, transport protocol number, source and destination portnumbers, flow label field in the IPv6 header, Security Parameter Index(SPI) in case of using IPv6 security (IPsec), destination prefix, typeof the multihomed mobile node interface associated to a care-of address,link characteristics on the communication link associated to a care-ofaddress.

Further, in a variation of this embodiment the home agent may receive atleast a part of the filter policies from the multihomed mobile node, aproxy acting on behalf of the multihomed mobile node or a policy controlnode in the home network or a foreign network.

In another embodiment of the invention the home agent performs a proxyneighbor discovery on behalf of the multihomed mobile node in responseto receiving the binding update. Moreover, there may be situations wherethe home agent has performed the proxy neighbor discovery on behalf ofthe multihomed mobile node prior to the multihomed mobile node attachingto the home network. The proxy neighbor discovery may for exampleinclude advertising the home agent's link layer address as the linklayer address of the multihomed mobile node.

According to another embodiment of the invention, the attachment of themultihomed mobile node to the home network comprises establishingcommunication bearers according to the radio access technology of thehome network for data exchange between the access system of the homenetwork and the multihomed mobile node. The communication bearers mayfor example be established prior to receiving the binding update at thehome agent.

The binding update may be received through a communication link in thehome network and/or a foreign network.

In some embodiments of the invention the binding update is received fromthe multihomed mobile node.

In other embodiments of the invention the binding update is receivedfrom a proxy in the home network. For example, the proxy may be locatedin the user plane data distribution path or the control plane data pathbetween home agent and multihomed mobile node.

In even other embodiments of the invention the binding update isreceived from a local mobility anchor in the home network handlingmobility of the multihomed mobile node within the home network. In thisembodiment, the binding update may indicate an address of the localmobility anchor for registration as a care-of address for the multihomedmobile node.

In some embodiments of the invention the home agent acts as a mobilityanchor for the multihomed mobile node when moving through differentnetworks.

Another embodiment of the invention provides a method for enablingsimultaneous use of a plurality of interfaces by a multihomed mobilenode being attached to a home network through one of the plurality ofinterfaces and to at least one foreign network through at least anotherinterface of the plurality of interfaces. The multihomed mobile node ora proxy acting on behalf of the multihomed mobile node initiate theregistration of an address in the home network to which the multihomedmobile node has attached as a care-of address for the multihomed mobilenode in the home network at a home agent serving the multihomed mobilenode in the home network. As mentioned above, the address to beregistered as a care-of address for the multihomed mobile node in thehome network is a home address of the multihomed mobile node in the homenetwork or an address of a network node located in the home network.Further, in response to the registration of the address as a care-ofaddress for the multihomed mobile node the multihomed mobile node or itsproxy may receive network layer packets through the home network and theat least one foreign network. Hence, the network layer packets destinedto the multihomed mobile node may be provided to same through its homenetwork and/or at least one foreign network.

As already indicated before, the registration of the address maygenerate a binding for the multihomed mobile node's home address in thehome network. The binding update may for example be sent via the homenetwork and/or the at least one foreign network. The registration of theaddress in the home network as a care-of address for the multihomedmobile node may for example be initiated by sending a binding update tothe home agent.

In a further embodiment of the invention, the registration of theaddress in the home network as a care-of address for the multihomedmobile node may be initiated by requesting a network node or the proxyin the home network to send a binding update to the home agent on behalfof the multihomed mobile node.

Moreover, according to another embodiment of the invention, themultihomed mobile node or its proxy may ignore requests for a multihomedmobile node's link layer address by other communication nodes in thehome network.

In another embodiment of the invention, the multihomed mobile node orits proxy may indicate the home agent's link layer address to at leastone other communication node in the home network in response to requestsfor the multihomed mobile node's link layer address by the at least oneother network node in the home network or the proxy.

According to another embodiment of the invention the multihomed mobilenode or the proxy may trigger the home agent to perform proxy neighbordiscovery functions on behalf of the multihomed mobile node upon havingattached to the home network. This could for example be accomplished bya binding update sent by the multihomed mobile node or the proxy toregister the address in the home network as a care-of address for themultihomed mobile node in the home network.

In a further embodiment of the invention, the multihomed mobile node orits proxy transmit filter policies to the home agent. The filterpolicies may be used by the home agent to determine which one or a partof a plurality of care-of addresses registered for the multihomed mobilenode and including the address in the home network is used to transmitor forward transport layer packets to the multihomed mobile node.

In another embodiment of the invention, the proxy and/or said networknode located in the home network is located on the data distributionpath between home agent and multihomed mobile node in the home network.

Further, it should be noted that the network node located in the homenetwork may also be the same network node or functional entity as theproxy acting on behalf of the multihomed mobile node.

Generally, a foreign network or the home network is for example any of a3GPP based network, a non-3GPP based wireless network, a WiMAX network,a Bluetooth network, a wireless packet-switched network or a fixedpacket-switched network. The address, the home address and care-ofaddresses may for example be network layer addresses, such as IPv6addresses. Hence, in some embodiments of the invention, the networklayer is implemented by the IPv6 protocol and at least the multihomedmobile node and the home agent implement the Mobile IPv6 protocol.

Another embodiment of the invention relates to a home agent serving amultihomed mobile node in a home network of the multihomed mobile nodeupon attachment of a multihomed mobile node to the home network. Thehome agent may include a receiver for receiving a binding update forregistering an address in the home network as a care-of address for themultihomed mobile node. This address to be registered as a care-ofaddress for the multihomed mobile node in the home network may forexample be a home address of the multihomed mobile node in the homenetwork or an address of a network node being located in the homenetwork. Further, the home agent may comprise a processing means, suchas a processor, for adding the home address of the multihomed mobilenode or the address of the network node located in the home network as acare-of address to a binding cache maintained by the home agent.

In another embodiment of the invention the home agent is configured toperform the steps of the method performed by the home agent according toone of the various embodiments and variations thereof described herein.

Further, another embodiment of the invention relates to a multihomedmobile node for enabling simultaneous use of a plurality of interfacesby a multihomed mobile node being attached to a home network through oneof the plurality of interfaces and to at least one foreign networkthrough at least another interface of the plurality of interfaces. Themultihomed mobile node may comprise a processing means for initiatingthe registration of an address in the home network to which themultihomed mobile node has attached as a care-of address for themultihomed mobile node in the home network at a home agent serving themultihomed mobile node in the home network. This address to beregistered as a care-of address for the multihomed mobile node in thehome network may for example be a home address of the multihomed mobilenode in the home network or an address of a network node being locatedin the home network. Further, the multihomed mobile node may have areceiver for receiving network layer packets through the home networkand the at least one foreign network in response to the registration ofthe address as a care-of address for the multihomed mobile node.

The multihomed mobile node according to another embodiment of theinvention is further operable to perform the steps of the method forenabling simultaneous use of a plurality of interfaces by a multihomedmobile node according to one of the various embodiments and variationsthereof described herein.

Moreover, another embodiment of the invention provides a proxy of amultihomed mobile node for enabling simultaneous use of a plurality ofinterfaces by a multihomed mobile node being attached to a home networkthrough one of the plurality of interfaces and to at least one foreignnetwork through at least another interface of the plurality ofinterfaces. The proxy may comprise a processing means for initiating theregistration of an address in the home network to which the multihomedmobile node has attached as a care-of address for the multihomed mobilenode in the home network at a home agent serving the multihomed mobilenode in the home network and a receiver for receiving network layerpackets through the home network in response to the registration of theaddress as a care-of address for the multihomed mobile node. Thisaddress to be registered as a care-of address for the multihomed mobilenode in the home network may for example be a home address of themultihomed mobile node in the home network or an address of a networknode being located in the home network.

According to another embodiment of the invention, the proxy is furtheroperable to perform the steps of the method for enabling simultaneoususe of a plurality of interfaces by a multihomed mobile node accordingto one of the various embodiments and variations thereof describedherein.

Even further, another embodiment of the invention relates to a computerreadable medium storing instructions that, when executed by a processorof a home agent serving a multihomed mobile node in a home network ofthe multihomed mobile node upon attachment of a multihomed mobile nodeto the home network, cause the home agent to receive a binding updatefor registering an address in the home network as a care-of address forthe multihomed mobile node, wherein the address to be registered as acare-of address for the multihomed mobile node in the home network is ahome address of the multihomed mobile node in the home network or anaddress of a network node located in the home network and to add theaddress as a care-of address to a binding cache maintained by the homeagent.

In another embodiment of the invention, the computer readable mediumfurther stores instructions that, when executed by the processor of ahome agent, cause the home agent to perform the steps of the methodperformed by the home agent according to one of the various embodimentsand variations thereof described herein.

Another embodiment provides a computer readable medium storinginstructions that, when executed by a processor of a multihomed mobilenode or a proxy acting on behalf of the multihomed mobile node, causethe multihomed mobile node or proxy to enable simultaneous use of aplurality of interfaces by the multihomed mobile node being attached toa home network through one of the plurality of interfaces and to atleast one foreign network through at least another interface of theplurality of interfaces, by initiating the registration of an address inthe home network to which the multihomed mobile node has attached as acare-of address for the multihomed mobile node in the home network at ahome agent serving the multihomed mobile node in the home network,wherein the address to be registered as a care-of address for themultihomed mobile node in the home network is a home address of themultihomed mobile node in the home network or an address of a networknode located in the home network and by receiving network layer packetsthrough the home network and the at least one foreign network inresponse to the registration of the address as a care-of address for themultihomed mobile node.

In another embodiment of the invention, the computer readable mediumfurther stores instructions that, when executed by the processor of amultihomed mobile node or the proxy acting on behalf of the multihomedmobile node, cause the multihomed mobile node or the proxy to performthe steps of the method for enabling simultaneous use of a plurality ofinterfaces by a multihomed mobile node according to one of the variousembodiments and variations thereof described herein.

BRIEF DESCRIPTION OF THE FIGURES

In the following the invention is described in more detail in referenceto the attached figures and drawings. Similar or corresponding detailsin the figures are marked with the same reference numerals.

FIG. 1 shows an exemplary network in which a multihomed mobile node hasregistered multiple care-of addresses at its home agent in themultihomed mobile node's home network,

FIG. 2 exemplarily illustrates the removing of all bindings in thebinding cache of the multihomed mobile node when returning home, thoughthe multihomed mobile node is still connected to a foreign network,

FIG. 3 exemplarily illustrates the multihomed mobile node registeringplural care-of addresses at the home agents binding cache according toan exemplary embodiment of the invention, wherein the care-of addressesinclude a home address local address,

FIG. 4 shows a more detailed overview of an exemplary systemarchitecture in which the invention may be implemented according to oneembodiment of the invention,

FIG. 5 shows an exemplary binding update message according to anembodiment of the invention,

FIG. 6 shows an exemplary binding unique identification sub-option thatmay be included in the binding update message of FIG. 5 according to anembodiment of the invention,

FIG. 7 shows an exemplary binding cache at an SAE anchor/home agentaccording to an exemplary embodiment of the invention,

FIG. 8 shows an exemplary neighbor cache maintained by an SAEanchor/home agent according to an exemplary embodiment of the invention,and

FIG. 9 shows an exemplary routing table maintained by an SAE anchor/homeagent according to an exemplary embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following paragraphs will describe various embodiments of theinvention. For exemplary purposes only, most of the embodiments areoutlined in relation to an (evolved) UMTS communication system accordingto the LTE discussed in the Background Art section above. It should benoted that the invention may be advantageously used for example inconnection with a mobile communication system such as the LTE UMTScommunication system previously described, but the invention is notlimited to its use in this particular exemplary communication network.

Accordingly, also the terminology used herein mainly bases on theterminology used by the 3GPP and by the IETF in the standardization ofMobile IPv6. However, the terminology and the description of theembodiments with respect to an LTE (UMTS) architecture and Mobile IPv6is not intended to limit the principles and ideas of the inventions tosuch systems and the use of this protocol only.

The explanations given in the Technical Background section above areintended to better understand the mostly LTE specific exemplaryembodiments described herein and should not be understood as limitingthe invention to the described specific implementations of processes andfunctions in the mobile communication network. Nevertheless, theimprovements proposed herein may be readily applied in thearchitectures/systems described in the Technological Background sectionand may in some embodiments of the invention also make use of standardand improved procedures of these architectures/systems.

Definitions

In the following a definition of several terms frequently used in thisdocument will be provided.

A network node or mobile node is a physical entity within a network. Onenode may have several functional entities. A functional entity refers toa software or hardware module that implements and/or offers apredetermined set of functions to other functional entities of a node orthe network. Nodes may have one or more interfaces that attach the nodeto a communication facility or medium over which nodes can communicate.Similarly, a network entity may have a logical interface attaching thefunctional entity to a communication facility or medium over which itmay communicate with other functional entities or nodes.

An address of a node or network entity is a global or site-localidentifier of the node or network entity being either of permanent ortemporarily limited validity. Typically, in some of the embodimentsherein an address is a network layer address, i.e., is used foridentification of nodes and network entities on the network layer of theOSI reference model (see for example the textbook “Computer Networks”,by Andrew S. Tanenbaum, fourth edition, 2003, Prentice Hall PTR, chapter1.4 incorporated herein by reference). The network layer or Layer 3typically provides the functional and procedural means for transferringvariable length packets from a source to a destination via one or morenetworks. In some embodiments of the invention, an address isidentifying a tunnel endpoint between a first network node/functionalentity and a second network node/functional entity, such as for examplean IP-over-IP tunnel or a GTP tunnel.

Typically, an interface of a host or a network node is assigned oneaddress. However, also multiple addresses may be assigned to a singleinterface. Further, in case of a network node comprising plural networkentities, an address may be associated to a logical interface of thenetwork entity.

A home address is an address assigned to a mobile node, used as thepermanent address of the mobile node. This address is within the mobilenode's home network. A mobile node may have multiple home addresses, forinstance when there are multiple home networks, or a mobile node mayhave multiple home addresses in a single home network.

A care-of address is an address associated with a mobile node whilevisiting a foreign network. A mobile node may have one or more care-ofaddresses simultaneously.

A home network of a mobile node is typically identified by the locationof the home agent at which the mobile node registers its care-ofaddress(es) for a given home address of the mobile node.

In some embodiments of the invention the IPv6 protocol is used on thenetwork layer. In this case the address is an identifier for a single(logical) interface of a host or network entity such that a packet sentto it from another IPv6 subnet is delivered via a lower-layer link tothe interface identified by that address.

A home agent is a router or a functional entity providing a routingfunction on a mobile node's home network with which the mobile noderegisters its current care-of address(es). While the mobile node is awayfrom home, the home agent may intercept packets on the home linkdestined to the mobile node's home address, encapsulate them, and tunnelthem to one of or some of the mobile node's registered care-ofaddress(es).

A binding is an association of the home address of a mobile node with acare-of address for that mobile node. in some embodiments of theinvention the remaining lifetime of that association and/or a bindingunique identification (BID) number (also referred to as binding uniqueidentifier) is also considered part of the binding. The binding uniqueidentification number is an identification number used to distinguishmultiple bindings registered by the mobile node. The assignment ofdistinct BID allows a mobile node to register multiple bindings for agiven mobile node (home address) while avoiding duplication of bindings.

Bindings are generated by way of registration which denotes a processduring which a mobile node or a proxy sends a binding update to themobile node's home agent (or a correspondent node), causing a bindingfor the mobile node to be registered. The bindings may for example bestored in a binding cache.

A multihomed mobile node is a mobile node that has several addresses tochoose between. For instance the multihomed mobile node may havemultiple interfaces and may be connected to different access networkssimultaneously.

Each network is identified by at least one number. This number allowsfor routing of packets to the nodes in the network. Furthermore, thisnumber refers to a pool of identifiers that can be used by the nodes inthe network. An address in a network is an identifier out of the pool ofidentifiers. For example in IPv6, the number of a network is the IPv6prefix and the address in a network is the IPv6 address composed of theIPv6 prefix and an IPv6 host part.

In different networks, for example in a home network and a foreignnetwork, different addresses are used.

Overview on the Invention

As has been explained above, the Mobile IPv6 protocol does not allow forusing a link to a foreign network and a link to a mobile node's homenetwork simultaneously. If the mobile node registers in the home networkby sending a binding update to the home agent, the home agent discardsall binding from the binding cache. Further, the home agent will stopperforming proxy neighbor discovery on behalf of the mobile node. Hence,in case a multihomed mobile node would be able to use another link to aforeign network for communication upon returning home (i.e., attachingto the access network of the home network) there are generally twooptions that a mobile node has: either the mobile node exclusively usedits link to the home network after having attached thereto, oralternatively it may not register itself at the home agent, so that alltraffic will still be routed to the mobile node using its care-ofaddress in the foreign network, i.e., exclusively through the foreignnetwork.

According to one aspect and embodiment of the invention it is suggestedthat a mobile node (or a proxy acting on behalf of the mobile node)registers an address in the home network as a care-of address for themultihomed mobile node at the home agent when the multihomed mobile nodeconnects or is connected to the home network. The address in the homenetwork registered as a care-of address for the multihomed mobile nodemay for example be the multihomed mobile node's home address in the homenetwork, the address of the proxy acting on behalf of the multihomedmobile node or the address of another network node or functional entityin the home network located in the data distribution path between homeagent and multihomed mobile node.

If for example Mobile IPv6 is used, the protocol may need to be extendedso as to allow the home agent to register a mobile node's home addressas a care-of address, which is presently not allowed according to theMobile IPv6 protocol specified in RFC3775. Moreover, in some embodimentsof the invention the home agent may further act as a proxy for themobile node and perform proxy neighbor discovery for the mobile nodewhile the mobile node is connected/attached to its home network.

In order to enable the use of several links (including that to themobile node's home network) another aspect and embodiment of theinvention relates to allowing the registration of more than one care-ofaddress in the binding cache of the home agent.

For distinction of individual bindings of a mobile node, one embodimentof the invention foresees to introduce a binding unique identificationnumber that is associated with an individual binding or a group ofbindings so as to allow the management (e.g., addition, deletion,update, etc.) of individual bindings in the binding cache. For thispurpose, another embodiment of the invention suggests an enhancedbinding update message of the Mobile IPv6 protocol specified in RFC3775.

FIG. 3 shows an exemplary network overview used for highlighting theseaspects of the invention. A multihomed mobile node is connected toforeign network #1 and has attached to its home network. For exemplarypurposes, home network and foreign network are both interconnectedthrough another packet switched network or networks, such as theinternet or a packet data network (PDN). In the exemplary embodimentshown in FIG. 3, a multihomed mobile node implementing a mobilitymanagement protocol (such as Mobile IPv6) is moving from foreign network#1 to its home network.

It should be noted that the home network may also be provided withanother mobility management protocol that is specific to the homenetwork and that handles mobility between networks of the same kindand/or within the access system of the home network. This is however notof essential interest for the principles of the invention.

Further, it is assumed in this example that the mobile node hasregistered a care-of address at its serving home agent in the homenetwork that is used to route data packets to the mobile node throughthe foreign network (using the care-of address).

Having attached to the home network (i.e., when having establishedconnectivity to the home network, e.g., to an access network of the homenetwork), the mobile node desires to maintain connectivity to theforeign network through a foreign link for communication. Hence, insteadof sending a binding update deregistering (all of) its care-ofaddress(es) at the home agent, the multihomed mobile node sends abinding update to the home agent that requests the home agent toregister the home address of the mobile node (in the home network) as acare-of address in the home network. Alternatively the binding updatemay also be sent by a proxy node in the home or foreign network onbehalf of the multihomed mobile node. Accordingly the binding update maybe transported to the home agent either through the home network or theforeign network to which it is connected. Further, as explained abovealso another address in the home network than the multihomed mobilenode's home address could be registered as a care-of address of themultihomed mobile node. For example, an address of a proxy in the homenetwork acting on behalf of the multihomed mobile node may be registeredaccording to another embodiment of the invention.

The home agent updates the binding cache in response to receiving thebinding update. As illustrated in FIG. 3 for exemplary purposes, a newbinding indicating the registration of the multihomed mobile node's homeaddress as a care-of address is added to the binding cache of the homeagent. The binding updates for registering the multihomed mobile node'scare-of address(es) may comprise a BID for distinguishing and/oridentifying individual bindings of the multihomed mobile node. Bydetecting the registration of the multihomed mobile node's home addressor an address in the home network (for example by the address prefix) asa care-of address the home agent may further recognize from the bindingcache entries for the multihomed mobile node that the multihomed mobilenode is connected to the home network and simultaneously to anotherforeign network.

Having registered the new binding for the multihomed mobile node (e.g.,the home address has been registered as a care-of address in the homenetwork), the home agent may now route data packets destined to themultihomed mobile node either through the home network or the foreignnetwork. Which network to choose for data delivery may for example bedecided based on filter rules or policies at the home agent.

In a variation of this embodiment, the home agent may act as a proxy forthe multihomed mobile node concerning neighbor discovery in the homenetwork. This means that the home agent answers requests for themultihomed mobile node link layer address and by indicating its own linklayer address to the requesting nodes or entity so that the data packetsdestined to the network layer address of the multihomed mobile node willbe forwarded to the home agent's link layer address. In anothervariation of the embodiment, a proxy acting on behalf of the multihomedmobile node performs neighbor discovery functions for the multihomedmobile node upon having registered a care-of address in the homenetwork. Similar to the variation described before the proxy providesthe link layer address of the home agent when answering requests for themultihomed mobile node link layer address.

Generally, the registration of the home address of a mobile node or anaddress in the home network as a care-of address for the multihomedmobile node within the home network may already be sufficient to enablethe mobile node to receive data not only through its home network butalso through a potentially further (foreign) network.

However, in some embodiments of the invention it has to be furtherensured that appropriate measures are foreseen in the home network so asto ensure a correct routing of data packets destined to the mobile nodethrough its home network. In these embodiments of the invention, anupdate of the distribution path of user plane data packets destined tothe multihomed mobile node may be foreseen in order to deliver the datapackets to the multihomed mobile node through the home network. Thisupdate of the distribution path may for example be accomplished byupdating the routing in the home network by an appropriate manipulationof routing or switching entries.

Overview of an Exemplary Network Architecture

FIG. 4 shows an overview of an exemplary network architecture in whichthe invention may be implemented. In this example, the home network ofthe multihomed mobile node 406 is separated into a core network, such as3GPP evolved packet core network 400, and a radio access network, suchas LTE radio access network (RAN) 401. In the radio access networkplural base stations, such as enhanced Node Bs, may be provided toprovide connectivity to the mobile nodes via an air interface.

The 3GPP evolved packet core network 400 comprises an inter accesssystem anchor (IASA) that is a functional entity in the evolved 3GPParchitecture. The entity may be logically split into an SAE anchor 402and a 3GPP anchor 403. In FIG. 4, the IASA is not depicted, but itsfunctional entities (SAE anchor 402 and a 3GPP anchor 403) are shown.The IASA may for example be responsible for the following functions:

-   -   Packet routing and forwarding;    -   Authentication, authorization and key management, for mobility        management signaling or for PDN access control (optional);    -   Policy and Charging Enforcement Function (PCEF);    -   Collection of Charging Information for online or offline        charging systems;    -   Mobility Anchor for mobility between 3GPP accesses and non-3GPP        accesses;    -   Gateway functionality to PDN including IP address allocation        from PDN address space;    -   Inter-3GPP access system mobility anchor (optional).

The SAE anchor 402 is a functional entity that anchors the user planefor mobility between 3GPP access systems and non-3GPP access systems. Inthis exemplary embodiment, the home agent is collocated with the SAEanchor 402 of the multihomed mobile node 406, i.e., either compriseshome agent functionality or the functional entities of SAE anchor 402and home agent are provided in a single network node.

The 3GPP anchor 403 is a functional entity that anchors the user planefor mobility between the 2G/3G access systems and the LTE access systemand is thus also responsible for routing the data packets destinedto/received from mobile nodes attached to the radio access network. Itis assumed that the 3GPP anchor is an anchor for user plane trafficfrom/to mobile nodes attached to the LTE RAN.

Further, the core network comprises at least one mobility managemententity 404. A mobility management entity (MME) manages and stores thecontext information for the mobile nodes (referred to as UEs in the 3GPPterminology). For example, when in idle state the UE/user identities, UEmobility state, and user security parameters are maintained in thecontext of the MME. The MME may further generate temporary identitiesand allocate them to mobile nodes/UEs. It may further check theauthorization whether the mobile node/UE may camp on the tracking area(TA) or on the public land mobile network (PLMN) and may alsoauthenticate user. The main MME functions may thus be summarized as:

-   -   Management and storage of UE control plane context;    -   Mobility management of UEs in the LTE RAN;    -   Authentication, authorization (PLMN, TA) and key management.

Moreover, the core network further comprises one or more user planeentities 404. A user plane entity (UPE) terminates the downlink datapath for idle state UEs and triggers/initiates paging when downlink dataarrive for the UE. The UPE commonly manages and stores UE contexts,e.g., parameters of the IP bearer service or network internal routinginformation. It performs replication of the user traffic in case ofinterception. The main UPE functions are thus:

-   -   Packet routing and forwarding;    -   Ciphering termination for user plane traffic;    -   IP Header compression;    -   Inter-eNode B Mobility Anchor for user plane.

It should be noted that the functions assigned to the 3GPP anchor mayalso be distributed to the MME and/or the UPE and/or the SAE anchor.

Another embodiment of the invention further foresees the integration ofa localized mobility management scheme in the architecture shown in FIG.4. In order to hide mobility within an access network from themultihomed mobile node, a network-based, localized mobility managementcan be used. A protocol supporting network-based, localized mobility(also known as NetLMM) allows a mobile node to move around in alocalized mobility domain, changing the point of attachment within thedomain, but without recognizing the change at the network layer, andmaintaining seamless communication.

Two protocol entities are typically defined for NetLMM, a Mobile AccessGateway (MAG) and a Local Mobility Anchor (LMA). Further, there may bealso a set of messages defined that are exchanged between MAG and LMA.Together, these specifications may make mobility events transparent tothe mobile nodes at the network layer. For example when a mobile nodehands over from one MAG to another MAG, the new MAG sends a locationregistration to the LMA in order to inform the LMA about the newlocation of the mobile node.

A local mobility anchor (LMA) may for example be a router or afunctional entity in a network node providing routing functionality thatterminates connections to multiple Mobile Access Gateways, servicesmobility requests for mobile nodes moving within a NetLMM (Network-basedLocalized Mobility Management) system, and participates in the NetLMMprotocol exchange.

The LMA may thereby maintain reachability to a mobile node's addresswhile the mobile node moves around within the NetLMM infrastructure. TheLMA may be further responsible to maintain forwarding information forthe mobile nodes which includes a set of mappings to associate mobilenodes by their identifiers with their address information, associatingthe mobile nodes with their serving MAGs and the relationship betweenthe LMA and the MAGs. There may be one or more LMAs in a NetLMMinfrastructure.

A Mobile Access Gateway (MAG) is a router embedded in a device or afunctional entity therein that terminates a specific link layertechnology to which mobile nodes attach themselves. It terminates oneend of the MAG of the connection to one or more Local Mobility Anchorsand participates in the NetLMM protocol exchange. Typically a MAG is arouter/routing entity that a mobile node is attached to as the first hoprouter in the NetLMM infrastructure. The MAG may be connected to themobile node over some specific link provided by a link layer but theNetLMM infrastructure is agnostic about the link layer technology thatis used. Each MAG has its own identifier used in NetLMM protocolmessaging between the MAG and the LMA. The important interfaces betweenlink layer specific functions and the NetLMM function reside on the MAG.There may be multiple MAGs in a NetLMM infrastructure.

There are different possibilities how network-based, localized mobilitymanagement may be applied in an evolved 3GPP architecture and how theNetLMM entities may be mapped to the different 3GPP entities. Forexample:

-   -   The LMA may be collocated with the SAE anchor. Here the LMA may        be separated from the home agent or may be even combined with        the home agent;    -   The LMA may also be collocated with the 3GPP anchor;    -   The MAG may be collocated with the 3GPP anchor (in case LMA is        collocated with SAE anchor);    -   The MAG may be collocated with the UPE (in case LMA is        collocated with 3GPP anchor or SAE anchor);    -   The MAG may be collocated with the MME (in case LMA is        collocated with 3GPP anchor or SAE anchor).

Registration of Care-of Addresses

Format of the Binding Update

According to an exemplary embodiment of the invention the binding update(BU) message is used by a mobile node to notify other nodes of a newcare-of address for itself. According to one aspect of the invention abinding update may also indicate a mobile node's home address as acare-of address even if the mobile node is attached to its home network.If needed, the binding unique identifier sub-option including the BID ofa registration may be included in the binding update.

In one exemplary embodiment, MIPv6 is used for mobility management. Inthis embodiment, the binding update may be similar to the binding updatedefined in RFC 3775, Section 6.1.7. The structure of the binding updateas defined in MIPv6 is shown in FIG. 5.

The care-of address of the multihomed mobile node may be for examplespecified either by the source address field in the IPv6 header or by analternate care-of address option, if present. In contrast to standardMIPv6, the binding update is not silently discarded if the care-ofaddress appears as a home address in an existing binding cache entry.

In one embodiment of the invention, the home agent does not remove anypreviously registered binding for a mobile node when receiving a bindingupdate. In this embodiment, the home agent may register each bindingreceived without deleting previous bindings from the binding cache.Hence, multiple bindings (i.e., care-of address registrations) for amultihomed mobile node are possible.

To manage the bindings of a multihomed mobile node, the home agent couldfor example delete individual bindings (or all bindings) upon receivingan explicit request or upon expiry of the lifetime of a binding/thebindings. This could for example be implemented by adding an additionalflag to a binding update that indicates whether the care-of addressincluded in the binding update is registering a new binding or requeststhe deletion of the binding corresponding to the indicated address. Inanother exemplary implementation, the binding update message is notextended, but the registration of a care-of address is deleted by“registering” the care-of address again and setting the lifetime fieldto zero or any arbitrary value indicating that a deletion of a bindingfrom the binding cache is requested.

Alternatively, in another embodiment of the invention, the bindingupdate known from MIPv6 may be extended by a binding unique identifiersub-option. Further, the BID sub-option may be optionally included inthe binding acknowledgment, binding refresh request, or binding errormessages.

An exemplary BID sub-option according to one exemplary embodiment of theinvention is shown in FIG. 6. This exemplary sub-option may be added toone of the before-mentioned messages of the MIPv6 protocol. Inparticular the BID sub-option may for example be added as a mobilityoption (see FIG. 5) to a binding update.

The type value of the BID sub-option is set to indicate that a BIDsub-option is included in the binding update. The length value may beset to different values to indicate whether the C flag in the sub-optionis set or not. E.g., if this value is set to 4, the C flag is unset: ifit is set to 20 the C flag is set.

Binding Unique ID (BID) includes an identifier assigned to the bindingcarried in the binding update with this sub-option. For example, the BIDmay be 16-bit unsigned integer.

When the BID sub-option is included in a binding update, thePriority/Status field indicates the priority field assigned to eachbinding. The receiver may utilize this priority to determine whichbinding is used to deliver data packets destined to the multihomedmobile node to the multihomed mobile node. For example, thepriority/status could be an 8-bit unsigned integer. A value of zerocould for example indicate that no priority is assigned to the binding;the higher the value the higher the higher the priority of the binding.Further, it should be noted that the presence of the Priority/Statusfield could be optional.

When the binding unique identifier sub-option is included in a bindingacknowledgment, the Priority/status field may indicate the statuscorrespondent to each binding in a bulk registration mode. The mobilenode may thereby be informed on the registration status of each binding.The value of the status field may indicate whether a registration of abinding/bindings has been successful or not.

In some embodiments of the invention optional Care-of Address (C) flagof the BID sub-option may indicate that the mobile node can store acare-of address correspondent to BID in the binding unique identifiersub-option. This flag may for example be included to the BID sub-optionwhenever the multihomed mobile node sends multiple bindings in a singlebinding update, i.e., a bulk registration is requested.

Another field in the binding unique identifier sub-option may be theRemovable (R) flag that may for example be set for indicating that amobile node requests a home agent to remove the binding correspondent toBID, even if the binding update is not for de-registration. However, theinclusion of this flag may be implementation specific and is thusoptional.

In another embodiment of the invention, the binding update may furtherinclude IP flow filter information that define filter policies accordingto which the home agent may decide which binding to use for forwardingor transmitting data packets destined to the multihomed mobile node.

FIG. 7 shows an exemplary binding cache at an SAE anchor/home agentaccording to an exemplary embodiment of the invention. In the left-handcolumn of the binding cache the multihomed mobile node for which thebinding in a respective row of the table is valid is indicated by itshome address for which the home agent serves the respective multihomedmobile node in the home network. For example, the first three bindingsin the table are associated to a first multihomed mobile node that has ahome address HoA#1. The 4th and 5th binding are for another, secondmultihomed mobile node having a home address HoA#2. For each binding thebinding cache indicates an associated care-of address. For the first twobindings for multihomed mobile node with home address HoA#1, two care-ofaddresses CoA#1 and CoA#2 in foreign networks are present. The 3rdbinding of multihomed mobile node with home address HoA#1 is indicatingthe multihomed mobile node's home address HoA#1 as its care-of address.Hence, this entry is a binding of the multihomed mobile node for its ownhome network served by the home agent maintaining the binding cache.

For the multihomed mobile node with HoA#2, two care-of addresses CoA#3and CoA#4 have been registered, which indicated that the multihomedmobile node has connectivity to two foreign networks.

Further, each binding may optionally contain a lifetime field thatindicates a number of time units remaining before the binding isconsidered expired by the home agent. Optionally each binding comprisesa home registration flag that indicates, when set, that the home agentshould act as the multihomed mobile node's home agent. Further, abinding may comprise a sequence number field that may be used to controlthe reception of binding updates. Further optionally, a binding maycomprise usage options.

As explained above, in some embodiments of the invention a bindingfurther comprises a BID field to manage individual bindings of amultihomed mobile node. Moreover, another optional field in a bindingmay be the priority of a binding. The priority may for examplefacilitate the selection of a binding out of the bindings registered fora multihomed mobile node to transmit, relay or forward data packetsdestined to the multihomed mobile node's home address using the care-ofaddress of the selected binding. Further, a binding may optionallycomprise filter information that may be used by the home agent to decidewhich binding(s) to use to transmit, relay or forward data packetsdestined to the multihomed mobile node's home address. In a variationalso the priority assigned to the bindings may be taken into accountwhen making this decision.

Registration of the Care-of Address

According to one embodiment of the invention, the multihomed mobile noderegisters its own home address in the home network as a care-of addressusing a binding update. This may for example be accomplished using MIPv6signaling over the home network (e.g., through the home network's accessnetwork). The home address of the multihomed mobile node is thusregistered as a care-of address for the home address of the multihomedmobile node.

Alternatively in another embodiment of the invention, the binding updatemay also include the multihomed mobile node's link layer networkconformant link-layer address. The home agent may then forward packetsdestined for the home link interface to this link layer address.

Another embodiment of the invention foresees that the binding updateincludes an identifier of a network node/functional entity within thehome network. For example, such network node/functional entity could bea UPE or a 3GPP anchor in the 3GPP evolved packet core network 400 (seeFIG. 4) or a proxy acting on behalf of the multihomed mobile node. Theidentifier of the network node may be for example known to the mobilenode as a result of the attachment procedures upon connecting to thehome network or as a result of the tracking area update procedure duringmobility. If using NetLMM, possible network nodes/functional entitiesmay for example be the LMA or MAG.

The identifier may be an address of the respective networknode/functional entity such as for example an IPv6 address or a linklayer address of the respective network node/functional entity.

Transmission of the Binding Update

In some embodiments of the invention, the binding update is transmittedvia the home network to the home agent. In another embodiment of theinvention the binding update is transmitted through a foreign network towhich the multihomed mobile node is attached. Further, if the multihomedmobile node sends the binding update the binding update may besimultaneously sent via more than one network to the home agent, e.g.,through the home network and at least one further foreign network orthrough two or more foreign networks.

As indicated above the binding update may be sent by the multihomedmobile node. Another option is that a network node/functional entityacting as a proxy for the multihomed mobile node transmits the bindingupdate to the home agent.

Thereby, the multihomed mobile node may either explicitly request thenetwork node/functional entity to do so. Alternatively, the sending ofthe binding update by a proxy may be implicitly triggered by signalingbetween the multihomed mobile node and the proxy or by the proxyreceiving a trigger from another network node/functional entity in thehome network or a foreign network.

In an embodiment of the invention, one proxy entity that may act onbehalf of the multihomed mobile node when sending the binding update isthe 3GPP anchor. For example, the multihomed mobile node couldexplicitly or implicitly request the 3GPP anchor to send the bindingupdate upon having attached to the access network of the home network,e.g., the LTE RAN 401 in FIG. 4. In another alternative embodiment ofthe invention, the binding update may also be sent by the MME or UPEupon explicit or implicit request from the multihomed mobile node.

In the examples above, MME or UPE (respectively) may also trigger thetransmission of the binding update on behalf of the multihomed mobilenode. This may for example be feasible if the multihomed mobile nodedoes not implement MIPv6 but UPE or MME act as a proxy for themultihomed mobile node as specified in “Network Based Layer 3Connectivity and Mobility Management for IPv6”, February 2006, byChowdhury et al., available at http://www.ieff.org, incorporated hereinby reference. According to this document and this example, themultihomed mobile node may connect to a target base station (such as aneNode B) in an inter access router handoff after having updated thebinding. However, in the SAE anchor and the access network, such as theLTE RAN, the multihomed mobile node is connected before its binding isupdated by means of a binding update.

Another embodiment of the invention relates to cases where NetLMM isused in the home network for localized mobility management, i.e., homenetwork wide mobility management. In this case the LMA as a network nodeor functional entity could send the binding update on behalf of themultihomed mobile node.

In one example, the LMA is a functional entity collocated with the SAEanchor. In this exemplary case, the mobile node may initiate thetransmission of the binding update from the LMA to the home agent alsobeing a functional entity in the SAE anchor via an SAE anchor internalinterface. Alternatively, if a proxy acts on behalf of the multihomedmobile node, the 3GPP anchor in the home network may trigger the sendingof the binding update by the LMA on behalf of the multihomed mobile nodeupon receiving an explicit or implicit trigger.

If the LMA is a functional entity collocated with 3GPP anchor, a similarsolution as proposed above may be used where the 3GPP anchor, i.e., itsLMA function, sends the binding update.

Proxy Neighbor Discovery

In case the multihomed mobile node is away from home, i.e., is notattached to the home network where its home agent is located, the homeagent will perform proxy neighbor discovery functions for the multihomedmobile node. This means that the home agent answers requests forresolving the multihomed mobile node link layer address on behalf of themultihomed mobile node thereby indicating the home agent's link layeraddress to the requesting entity or node. Upon the multihomed mobilenode returning home, according to one embodiment of the invention, thehome agent performs proxy neighbor discovery functions for themultihomed mobile node. For example, upon receiving the binding updateindicating a care-of address of the multihomed mobile node in the homenetwork, the home agent may continue to act as a proxy for themultihomed mobile node and may answer neighbor solicitations forresolving the multihomed mobile node's link layer address by sending aneighbor advertisement including its link layer address.

Optionally, the binding update may contain a flag that indicates to thehome agent whether to perform neighbor discovery functions on behalf ofthe multihomed mobile node or not upon the multihomed mobile nodeattaching to its home network.

In another embodiment of the invention, the home agent stops performingneighbor discovery functions upon receiving a binding update for themultihomed mobile node having attached to the home network. In thisembodiment a proxy in the home network, for example 3GPP anchor 403 orUPE 405 in FIG. 4, may perform neighbor discovery functions on behalf ofthe multihomed mobile node. The same solution may also apply inscenarios where the multihomed mobile node does not implement MIPv6, but“Proxy MIP” as described in “Network Based Layer 3 Connectivity andMobility Management for IPv6” mentioned above is used.

In the embodiments described above, the multihomed mobile node may notbe answering neighbor solicitations when being connected to the homenetwork and having registered a care-of address in the home network.

Adaptation of the Data Path in the Home Network

In some embodiments of the invention, the data plane route of datapackets destined to the multihomed mobile node is updated upon theregistration of a care-of address for the multihomed mobile node in itshome network in response to the binding update. This may for examplerequire an update of the routing table/neighbor cache in SAE anchorcomprising the home agent.

In some embodiments of the invention the neighbor cache is a “table”that allows the resolution of a link layer address of the next hoptowards the multihomed mobile node when sending data packets to themultihomed mobile node through the home network or a foreign network.E.g., if the home agent has chosen one (or more) care-of address bymeans of which the link layer address of the next hop may be resolved.

Considering for exemplary purposes the architecture in FIG. 4, the homeagent in SAE anchor 402 could transmit or forward data packets to themultihomed mobile node through the home network (consisting of the 3GPPevolved packet core network 400 and the LTE RAN 401) or through theforeign network, i.e., non-3GPP based network/WLAN 3GPP IP network 410.If the home agent decides to utilize the care-of address of themultihomed mobile node 406 in the foreign network, it may resolve thelink layer address for the next link layer hop to gateway 411.

Assuming that SAE anchor 402 with the home agent and the gateway 410 areboth located within a common link layer network, the resolution willindicate the gateway 410 as the next hop on the link layer.

Alternatively, the routing table in the SAE anchor 402 may indicate tothe home agent a network layer address specifying the next hop on, e.g.,an IP based network that is interconnecting the home and foreignnetwork. By means of this network layer address the home agent mayresolve the link layer address of the next hop (e.g., router) byutilizing the neighbor cache maintained within the SAE anchor 402.

If deciding to transmit or forward data packets destined to themultihomed mobile node through the home network, the neighbor cachecould, e.g., indicate the link layer addresses of the 3GPP anchor 403 orUPE 405, so that—on the link layer—the data packets are provided to the3GPP anchor 403 or UPE 405, respectively, which then forward the datapackets further downstream to the multihomed mobile node, e.g., via aeNode B to which the multihomed mobile node is connected.

FIG. 8 shows an exemplary neighbor cache maintained by an SAEanchor/home agent according to an exemplary embodiment of the invention.As indicated therein, the neighbor cache may be considered a table thatis allowing to determine a link layer address of a next hop on the linklayer for a given network layer address. For example, if a network nodeor functional entity needs to send, forward or relay a network layerdata packet to a destination on the same link-layer network, it may lookup the link layer address of the destination network layer address inthe neighbor cache. For example, if an IP packet is to be sent to the IPaddress IP#2, the link layer protocol of the network node or functionalentity will look up the link layer destination address from the neighborcache and transmits the IP packet encapsulated in a link-layer packet tothe link layer address indicated in the neighbor cache.

In another embodiment, the network nodes in the 3GPP packet core network400 use the IP protocol on the network layer. In these cases it is alsopossible that the (IPv6) data packets the home agent is transmitting orforwarding are provided to the next hop on the user data path to themultihomed mobile node through IP-over-IP tunneling.

For example, if the downlink distribution path would be SAE anchor 402(home agent)→3GPP anchor 403→UPE 405→eNode B→multihomed mobile node 606,then the home agent may use an IP tunnel between SAE anchor 402/homeagent and the 3GPP anchor 403 to provide the data packets to the 3GPPanchor 403. For this purpose, the tunnel endpoint between home agent and3GPP anchor 402 should be registered as a care-of address for themultihomed mobile node 406 in the home network within the binding cache.Further, also between the 3GPP anchor 403 and UPE 405 an(other)IP-over-IP tunnel may be used for providing the packets from 3GPP anchor403 to UPE 405. Alternatively, the IP-over-IP tunnel may also beestablished between SAE anchor 402/home agent and UPE 405.

Concerning the connection between UPE 405 and the eNode B serving themultihomed mobile node 406 in LTE RAN 401, a GTP tunnel may be used fordata packet exchange. For more details on the known GTP protocol, see3GPP TS 29.060, “General Packet Radio Service (GPRS), GPRS TunnellingProtocol (GTP) across the Gn and Gp interface”, version 7.2.0 of June2006 incorporated herein by reference.

In another alternative embodiment of the invention, the downlinkdistribution path may be SAE anchor 402 (home agent)→UPE 405→eNodeB→multihomed mobile node 606 (i.e., there is a direct interface betweenSAE anchor 402 and UPE 405). In this case similar measures fortransmitting or forwarding the data packets destined to multihomedmobile node 406 as described above may be foreseen. In this casehowever, if using link layer transport between SAE anchor 402/home agentand UPE 405, the link layer address or network layer address of the UPE405 may be registered as a care-of address for the multihomed mobilenode 406. Alternatively, if the multihomed mobile node's home address isregistered in a care-of address, the routing table/neighbor cache in theSAE anchor 402/home agent indicates the UPE 405 as the next hop towardsthe multihomed mobile node 406.

FIG. 9 shows an exemplary routing table maintained by an SAE anchor/homeagent according to an exemplary embodiment of the invention. In thisexample, a mobile node has three connections, two connections to aforeign network (first two rows) and one connection to the home network(3rd row). Moreover, there is a default routing entry * in the last rowof the routing table.

The home agent sets up tunnels for the packets destined to CoA#1 andCoA#2. For this, virtual tunnel interfaces tun0 and tun1 may beestablished and the IP routing module forwards packets to CoA#1 or CoA#2to the virtual interface tun0 or tun1, respectively. The virtualinterface encapsulates the packets in IP with the IP address of the homeagent as source address and the care-of address as destination address.In the next step the IP-in-IP encapsulated packets are again forwardedto the IP routing module. The next hop for IP packets to the care-ofaddresses are forwarded to the default gateway indicated by the entry *in the last row.

Furthermore, in this example, the home agent and a proxy node acting onbehalf of the mobile node are on the same link. Packets for the MNdestined to HoA#1 in the home network are not tunnelled, they will beforwarded to the link layer of the real interface. The neighbor cacheentry of the link layer interface has an entry for the HoA#1 with thelink layer address for the proxy node.

If using NetLMM, the LMA (irrespectively of its actual physicallocation) may send the binding update for registering a home networklocal care-of address for the multihomed mobile node 406. In this casethe SAE anchor 402/home agent should register the address of the LMA asa care-of address for the multihomed mobile node 406 in the home networkso that data packets (if provided through the home network) areforwarded to the LMA. Alternatively, if the home address of themultihomed mobile node 406 is registered as a care-of address for themultihomed mobile node 406 in the home network, the routingtable/neighbor cache in the SAE anchor 402/home agent should beconfigured to indicate the LMA as the next hop on the distribution pathtowards the multihomed mobile node 406. As a result the distributionpath may look like SAE anchor 402 (home agent)→LMA→MAG→eNodeB→multihomed mobile node 606.

As becomes apparent from the explanations above, in some embodiments ofthe invention appropriate measures for configuring the user plane datatraffic to/from the multihomed mobile node 406 may be foreseen in thehome network. In general, irrespective of which local address isregistered as a care-of address for the multihomed mobile node by meansof a binding update sent to the home agent, the neighbor cache of theSAE anchor 402/home agent or its routing may be configured to indicatethe link layer address, network layer address of the next hop orappropriate tunnel endpoint towards the multihomed mobile node.

For this purpose in one embodiment of the invention the networknode/functional entity that is sending the binding update is eitherincluding appropriate update information for updating routing/neighborcache entries to the binding update or uses separate signaling toconfigure the updating routing/neighbor cache entries in SAE anchor402/the home agent and optionally further intermediate network nodes inthe distribution path to the multihomed mobile node. Another alternativeembodiment of the invention foresees that that the routing/neighborcache entries of the network nodes are configured in response to themultihomed mobile node's attachment to the access network of the homenetwork. For example in an architecture as shown in FIG. 4, the MME 404may be requested by the multihomed mobile node to act as a proxy for themultihomed mobile node 406 in the home network. Accordingly, MME 404 mayfor example send a binding update to the home agent registering anaddress (being either the home address of multihomed mobile node 406 orthe address of 3GPP anchor 402, UPE 405 or an LMA) as a care-of addressof the multihomed mobile node 406 in the home network or may request oneof the other network nodes/functional entities in the 3GPP packet corenetwork 400 to do so. Depending on which address has been registered andwhether a link layer or network layer address is registered as a care-ofaddress, MME 404 may further update or establish the data distributionpath through the home network by for example configuring therouting/neighbor cache entries at SAE anchor 402/home agent andoptionally the routing/neighbor cache entries in 3GPP anchor 403 and/orUPE 405.

Another embodiment of the invention relates to a system where NetLMM isused in the home network. In this example the LMA function, the homeagent function as well as the SAE function are located in a singlenetwork node, referred to as the SAE anchor in this example. Hence, inthis case several functional entities are collocated in a single networkelement. Also in this exemplary embodiment similar mechanisms asdescribed above may be used, since the different functional entities maybe provided with virtual interfaces and identifiers so that data arerelayed from one entity to another in the network element. Furthermore,the individual entities may directly alter (e.g., add, change, delete,update, etc.) settings and/or entries in the neighbor cache, bindingcache and/or routing table within the SAE anchor. Hence, instead of onefunctional entity triggering the modifications to be performed by arespective other functional entity by means of internal signaling, thefunctional entities may directly modify the settings and/or entries inthe neighbor cache, binding cache and/or routing table within the SAEanchor as needed.

Data Transmission to the Multihomed Mobile Node

In several embodiments above, the multihomed mobile node is not onlyconnected to the home network but also to at least one foreign network.Accordingly in these embodiments there may be several care-of addressesregistered for the multihomed mobile node at the home agent. If the homeagent needs—for example—to forward data packets of a service (OperatorIP Services, e.g., IMS, PSS; etc.) that origins from other packetswitched network(s) 421 such as PDN, Internet, etc., the home agent hasmultiple care-of addresses to choose for forwarding the data.

Another embodiment foresees that the home agent determines which care-ofaddress or which subset of registered care-of addresses to use toforward the data packets. The decision may for example be based onfilter policies. These filter policies may for example include at leastone of user preferences, network operator preferences, source anddestination IP addresses, transport protocol number, source anddestination port numbers, flow label field in the IPv6 header, SecurityParameter Index (SPI) in case of using IPv6 security (IPsec),destination prefix, type of the multihomed mobile node interfaceassociated to a care-of address, link characteristics on thecommunication link associated to a care-of address.

Hence, if for example the home network is a 3GPP-based UMTS network thevoice data of a video conferencing session may be provided to themultihomed mobile node through the UMTS network, while the video data ofthe video conferencing session may be routed by the home agent through aforeign network to which the multihomed mobile node is connected andthat is capable of providing a broadband services, e.g., a WLAN or WiMAXnetwork. Accordingly, the home agent may use the registrations ofmultiple bindings to provide services like load sharing or loadbalancing. Further, this may also enable the support of preferencesettings that could allow a user, the application or a service providerto choose the preferred transmission technology or access network basedon cost, efficiency, policies, bandwidth requirement, delay, etc.

Software and Hardware Implementation

Another embodiment of the invention relates to the implementation of theabove described various embodiments using hardware and software. It isrecognized that the various embodiments of the invention may beimplemented or performed using computing devices (processors). Acomputing device or processor may for example be general purposeprocessors, digital signal processors (DSP), application specificintegrated circuits (ASIC), field programmable gate arrays (FPGA) orother programmable logic devices, etc. The various embodiments of theinvention may also be performed or embodied by a combination of thesedevices.

Further, the various embodiments of the invention may also beimplemented by means of software modules, which are executed by aprocessor or directly in hardware. Also a combination of softwaremodules and a hardware implementation may be possible. The softwaremodules may be stored on any kind of computer readable storage media,for example RAM, EPROM, EEPROM, flash memory, registers, hard disks,CD-ROM, DVD, etc.

It should be further noted that the individual features of the differentembodiments of the invention may individually or in arbitrarycombination be subject matter to another invention.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiments without departing from the spirit orscope of the invention as broadly described. The present embodimentsare, therefore, to be considered in all respects to be illustrative andnot restrictive.

1. A home agent for enabling a user equipment having a plurality ofinterfaces to simultaneously use a home link and a foreign link, whereinthe same home address of the user equipment is used for packetstransferred through the plurality of interfaces, the home agent of theuser equipment comprising: a communication unit configured to receive abinding update message from the user equipment, when the user equipmenthas connected to both the home link and the foreign link, wherein thebinding update message contains the home address of the user equipmentin the home link within a care-of address field of the binding updatemessage, and wherein the home agent is configured to register inresponse to receiving the binding update message a binding between theuser equipment's home address and the care-of address indicated in thebinding update message, the indicated care-of address being the homeaddress of the user equipment, in a binding entry.
 2. The home agentaccording to claim 1, wherein the binding update message registers abinding between the user equipment's home address and the care-ofaddress indicated in the binding update message, the indicated care-ofaddress being the home address of the user equipment, wherein thebinding is registered together with another binding between the userequipment's home address and a care-of address configured in the foreignlink.